From PCGamesN: “Looking for Golden Seeds in Elden Ring? These handy seeds allow you to upgrade your flasks, increasing the uses of Crimson and Cerulean Flasks to help you out when you come up against tough Elden Ring bosses or explore one of Elden Rings many dungeons.
They can be found across the Lands Between; you can spot them by glowing Erdtree saplings, which make them easy to see from a distance when traversing the expansive open world. To use Golden Seeds, simply rest at a Site of Grace and charge your flask, with each upgrade increasing the amount of Golden Seeds required by one. You can also choose Golden Seed as a Keepsake when youre picking your Elden Ring class during the character creation. You can upgrade your flask ten times and also strengthen them by finding and using Sacred Tears.”